A study has found that children who take part in more than 17 hours of extracurricular activities a week could be harming their educational prospects.

Researchers have argued parents hoping to raise rounded offspring by enrolling children in ballet classes or piano lessons may be exposing them to increased stress.

Instead of filling their children’s free time with extracurricular pursuits, families have been urged to encourage an equal amount of “free play” as well.

Jennifer Fredricks, associate director of human development at Connecticut College found that the positive effects of one to 13 hours of weekly extracurricular activies were clear in children’s exam performance.

But for students taking part in more than 17 hours of lessons, clubs and classes outside school, their grades and overall well-being notably dropped.

“Above a certain level, you see a decline in grades and a decline in achievement,” the Daily Mail quoted Fredricks as telling the Sunday Times.

Her team monitored the activities of 10,000 15-and 16-year-old students across the U.S and found a seemingly optimum amount of extracurricular activities.

Pupils who took part in five activities a week scored an average of 56 per cent in maths exams, higher than their classmates with fewer extracurricular engagements.

But for students spending more free time on non-academic pursuits, exam results were found to fall.

Pupils with more than 10 extracurricular activities a week had a four per cent lower grade average than normal and even achieved worse results than school friends who had no organised pursuits outside school.